Bottom Line:
We examined historical effects on FCL in large lakes spanning >6 orders of magnitude in age.We found that food chains in the world's ancient lakes (n = 8) were significantly shorter than in recently formed lakes (n = 10) and reservoirs (n = 3), despite the fact that ancient lakes harbored much higher species richness, including many endemic species.Our results highlight a counter-intuitive and poorly-understood role of evolutionary history in shaping key food web properties such as FCL.

ABSTRACTFood webs may be affected by evolutionary processes, and effective evolutionary time ultimately affects the probability of species evolving to fill the niche space. Thus, ecosystem history may set important evolutionary constraints on community composition and food web structure. Food chain length (FCL) has long been recognized as a fundamental ecosystem attribute. We examined historical effects on FCL in large lakes spanning >6 orders of magnitude in age. We found that food chains in the world's ancient lakes (n = 8) were significantly shorter than in recently formed lakes (n = 10) and reservoirs (n = 3), despite the fact that ancient lakes harbored much higher species richness, including many endemic species. One potential factor leading to shorter FCL in ancient lakes is an increasing diversity of trophic omnivores and herbivores. Speciation could simply broaden the number of species within a trophic group, particularly at lower trophic levels and could also lead to a greater degree of trophic omnivory. Our results highlight a counter-intuitive and poorly-understood role of evolutionary history in shaping key food web properties such as FCL.

pone-0037856-g001: Food-chain length in lakes of different origins and age.A) Boxplot for food-chain length in lakes of different origins. Symbols represent the median FCL, boxes = inter-quartiles, and bars = maximum and minimum values. Different letters indicate significant differences by multiple comparison using ANOVA (p<0.001). B) Correlation between age of lake and food-chain length. Different symbols are for reservoir, glacial and ancient lakes (see A). Lake Victoria and Lake Kyoga are originally from 400,000 years ago, but are thought to have dried up 14,600 years ago.

pone-0037856-g001: Food-chain length in lakes of different origins and age.A) Boxplot for food-chain length in lakes of different origins. Symbols represent the median FCL, boxes = inter-quartiles, and bars = maximum and minimum values. Different letters indicate significant differences by multiple comparison using ANOVA (p<0.001). B) Correlation between age of lake and food-chain length. Different symbols are for reservoir, glacial and ancient lakes (see A). Lake Victoria and Lake Kyoga are originally from 400,000 years ago, but are thought to have dried up 14,600 years ago.

Mentions:
Symbols mean the origin of lakes as Fig.1A.

Bottom Line:
We examined historical effects on FCL in large lakes spanning >6 orders of magnitude in age.We found that food chains in the world's ancient lakes (n = 8) were significantly shorter than in recently formed lakes (n = 10) and reservoirs (n = 3), despite the fact that ancient lakes harbored much higher species richness, including many endemic species.Our results highlight a counter-intuitive and poorly-understood role of evolutionary history in shaping key food web properties such as FCL.

ABSTRACTFood webs may be affected by evolutionary processes, and effective evolutionary time ultimately affects the probability of species evolving to fill the niche space. Thus, ecosystem history may set important evolutionary constraints on community composition and food web structure. Food chain length (FCL) has long been recognized as a fundamental ecosystem attribute. We examined historical effects on FCL in large lakes spanning >6 orders of magnitude in age. We found that food chains in the world's ancient lakes (n = 8) were significantly shorter than in recently formed lakes (n = 10) and reservoirs (n = 3), despite the fact that ancient lakes harbored much higher species richness, including many endemic species. One potential factor leading to shorter FCL in ancient lakes is an increasing diversity of trophic omnivores and herbivores. Speciation could simply broaden the number of species within a trophic group, particularly at lower trophic levels and could also lead to a greater degree of trophic omnivory. Our results highlight a counter-intuitive and poorly-understood role of evolutionary history in shaping key food web properties such as FCL.